Real-time MAC Protocol Research Articles

A two-channel slotted sense multiple access protocol for timely and reliable data transmission in industrial wireless sensor networks

In designing a real-time MAC protocol for wireless sensor networks, it is desirable to shorten the data acquisition cycle time to satisfy more applications with a tighter time constraint in data collection. To achieve this, one often tries to improve throughput by employing a slot reuse technique. Meanwhile, the slotted sense multiple access protocol that uses a sharable slot was proven to be advantageous for timely and reliable data delivery. However, since the nodes at lower tree levels process more packets or bigger packets with data aggregation, they need a bigger sharable slot. Thus, it is not easy to employ a slot reuse technique due to the size variation of sharable slots. To tackle this problem, we try to reduce the size of an aggregated packet by limiting the number of packets for aggregation using two channels. If every node is allowed to send a single packet during data acquisition cycle time, an equal-sized sharable slot can be allocated to every tree level. It is shown that the proposed approach can reduce data acquisition cycle time significantly while maintaining good reliability in data transmission compared with slotted sense multiple access and also reduce energy consumption greatly compared with another multi-channel MAC protocol.

A Real-time MAC Protocol for Event-driven Wireless Sensor Networks

A Real-time MAC Protocol for Event-driven Wireless Sensor Networks

Evaluating the benefits and feasibility of coordinated medium access in MANETS

Mobile ad hoc wireless network (MANETs) are characterized by a highly-dynamic topology where neither the duration of links between nodes nor their densities within the network can be foreseing. To better understand the effects of such issues in the medium access we provide a performance evaluation of two distinct MAC protocols. The first is our previously proposed HCT (Hybrid Contention/TDMA) Real-Time MAC protocol, which continuously adapts to topology modifications in order to provide a kind of coordinated medium access. Its performance is compared with a contention-based, non-coordinated CSMA protocol, which is the typical MAC protocol used in MANETs. We analyze both protocols with respect to their ability to deliver messages in a timely manner. More specifically, we compared the ratio of messages delivered within their deadlines and the medium utilization provided by these protocols. Such aspects where analyzed considering mobile networks with different spatial densities and speeds of nodes. This study also addresses the protocols overhead, especially for HCT-MAC. Obtained results show that HCT-MAC appears as a good solution for applications like search-and-rescue, autonomous highway driving (platooning), and multimedia, which require some kind of QoS guarantee in respect to the timely delivery of messages.

A Survey on Real-Time MAC Protocols in Wireless Sensor Networks

As wireless sensor network becomes pervasive, new requirements have been continuously emerged. How-ever, the most of research efforts in wireless sensor network are focused on energy problem since the nodes are usually battery-powered. Among these requirements, real-time communication is one of the big research challenges in wireless sensor networks because most of query messages carry time information. To meet this requirement, recently several real-time medium access control protocols have been proposed for wireless sensor networks in the literature because waiting time to share medium on each node is one of main source for end-to-end delay. In this paper, we first introduce the specific requirement of wireless sensor real-time MAC protocol. Then, a collection of recent wireless sensor real-time MAC protocols are surveyed, classified, and described emphasizing their advantages and disadvantages whenever possible. Finally we present a dis-cussion about the challenges of current wireless sensor real-time MAC protocols in the literature, and show the conclusion in the end.

A new real-time ethernet MAC protocol for time-critical applications

The authors propose a new persistent transmission-based real-time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real-time frames. Moreover, it is compatible with the protocol used by the existing Ethernet controllers for conventional datagram traffic and thus standard Ethernet stations can be used in the system without any modification. The paper describes the protocol in detail and analyses the maximum delivery delay for real-time traffic and the efficiency of the channel.

A distributed real-time MAC protocol for WDM-based LANs

In this paper, we consider the problem of developing a MAC layer protocol to support real-time as well as non-real-time packet streams in Broadcast and Select WDM optical networks having rapidly tunable transmitters. We propose a MAC layer protocol which is the best-effort in nature and has two phases: demand notification phase and packet transmission phase. In the demand notification phase, a token circulates among the nodes in a round robin manner gathering the demand information of the traffic on each node. This information is recorded in the local status tables of each node. An algorithm is run on all the nodes in a distributed manner in order to resolve the contention for each channel. The contention resolution algorithm gives due weightage to both the real-time deadline of the streams of traffic and tuning time of the transmitter. In the proposed protocol, the traffic streams on any node are not bound to a physical channel and can use any channel onto which a receiver on the destination node is tuned. Also, the protocol attempts to overlap the transmitter tuning with the packet transmission in order to minimize the channel idle time due to transmitter tuning. We demonstrate the effectiveness of the proposed protocol through extensive simulation studies.